The present invention relates to diagnostic methods of detecting early immune activation by detecting the T-cell immune response cDNA 7 (TIRC7). In particular, the present invention provides TIRC7 as an early biomarker for the detection of transplant rejection in a noninvasive diagnostic method that replaces biopsy interventions with a simple diagnostic method for monitoring after transplantation. Furthermore, the present invention relates to kits for use in such methods of diagnosis.
T-cell activation is a serial process involving multiple signaling pathways and sequential changes in gene expression resulting in differentiation of T-cells into distinct subpopulations, i.e. Th1 and Th2, which are distinguishable by their pattern of cytokine production and characterize the mode of cellular immune response. The T-cell response is initiated by the interaction of the antigen-specific T-cell receptor (TCR) with a peptide presented by major histocompatibility complex (MHC) molecules on the surface of antigen presenting cells (APCs). Additional signals are provided by a network of receptor-ligand interactions mediated by a number of membrane proteins such as CD28/CTLA4 and B7, CD40/CD40L, LEA-I and ICAM-1 (Lenschow, Science 257 (1992), 789-792; Linsley, Annu. Rev. Immunol. 11 (1993), 191-212; Xu, Immunity 1 (1994), 423-431; Bachmann, Immunity 7 (1997), 549-557; Schwartz, Cell 71 (1992), 1065-1068) collectively called costimulatory signals (Perez, Immunity 6 (1997), 411-417). These membrane proteins can alter T-cell activation in distinct ways (Bachmann, Immunity 7 (1997), 549-557) and regulate the immune response by the integration of positive and negative signals provided by these molecules (Bluestone, Immunity 2 (1995), 555-559; Perez, Immunity 6 (1997), 411-417). Many of the agents which are effective in modulating the cellular immune response either interfere with the T-cell receptor (Cosimi, Transplantation 32 (1981), 535-539) block costimulatory signaling (Larsen, Nature 381 (1996), 434-438; Blazar J. Immuno. 157 (1996), 3250-3259; Kirk, Proc. Natl. Acad. Sci. USA 94 (1997), 8789-8794; Linsley, Science 257 (1992), 792-95; Turka, Proc. Natl. Acad. Sci. USA 89 (1992), 11102-11105) or inhibit intracellular activation signals downstream from these primary cell membrane triggers (Schreiber and Crabtree, Immunology Today 13 (1992), 136-42). Therapeutic prevention of T-cell activation in organ transplantation and autoimmune diseases presently relies on pan-immunosuppressive drugs interfering with downstream intracellular events. Specific modulation and detection of the immune response, e.g., in transplantation therapy remains a longstanding goal in immunological research.
For example, acute rejection (aRx) has a major impact on the long-term outcome of renal allografts, and its diagnosis is contingent on the invasive procedure of allograft biopsy. New immunosuppressive protocols have reduced the incidence but have not abolished this problem. Moreover, aRx is now more frequently seen several weeks after transplantation in outpatients. A non-invasive diagnostic test for predicting aRx could improve the management and outcome.
Hence, there is a the need of early biomarker and non-invasive diagnostic methods to detect activation of the immune response, in particular for conditions where activation of the immune response is related to a disease or disorder, for example transplant rejection.